1. Field of the Invention
The present invention relates to a resistance welding control method for supplying welding current to a workpiece to thereby perform welding.
2. Prior Art
In most cases, generation of particles of molten metal expelled or spattered during welding operation (hereinafter referred to as generation of spatter) becomes a criterion of judgment of satisfactory welding in a welding site, namely, the formation of a desired nugget. There is employed a method, as means for coping with the generation of spatter, that welding current is stopped from flowing or welding current is reduced after the detection of the generation of spatter.
When the resistance welding apparatus repeats welding operation, the electrode tip diameter is gradually expanded, thereby lowering the current densities at the welded portion, and hence some welding apparatus increases welding current, etc. as one of the welding conditions every moment with the lapse of time.
However, since the resistance welding is controlled in the prior art means, which is provided for coping with the generation of spatter after the generation of spatter is detected, there is a problem that this prior art means is not effective for preventing the generation of spatter so that a high welding quality can not be obtained and the welding site environment is deteriorated. In a system which has been widely used for several years for setting an increasing ratio of welding current arbitrarily by an operator, there is a problem that it is difficult to reduce the generation of spatter and meet the desired welding quality even by resorting to much experience and skills of the operator.